I have to respectfully agree, but disagree. Yes. Rodgers is the better QB, however, McCarthy transformed Rodgers into what he is today... McCarthy is one of the best QB coaches and I read that a few of his drills from his camp are used around the NFL today for all QBs.
McCarthy as an architect of QBs is way, way overstated.
First, when he was OC in SF he stumped for Alex Smith over Aaron Rodgers in the 2005 draft. So, we have him to thank for that. Smith was a mess until Harbaugh got him to play away from his weaknesses and fashioned him into a respectable system QB.
Second, Rodgers fell in the draft for what are typically thought to be too factors: 1) a too low key "California QB" demeanor and 2) poor mechanics.
Rodgers is still low key so McCarthy did not fix that "flaw".
As far as the bad mechanics, the rap was he held the ball high at the ear before cocking his arm, and the untoward things that follow from that. If you look at some of his college tape it does look old-school-dreadful. As it happens though, Rodgers has since mentioned that the correction to the pro-style form we see today was fairly easy for him...that's the way he threw in HS and at Chico...it was the goofy Cal coaches that wanted that ugly looking high hold.
McCarthy gets credit for developing Aaron Brooks in New Orleans. Check.
McCarthy gets credit for supervising Rodgers' self-corrections, maybe adding a few helpful tweeks. Whether McCarthy gets credit for keeping Rodgers focused while waiting on the bench with no clear end in sight is hard to say. Rodgers seem awfully focused on his own, and that's understating it. More like laser focused.
I don't mean to say McCarthy had nothing to do with Rodgers development. That would be foolish. But if anybody thinks Rodgers was some raw material molded in McCarthy's hands is way over-stating the case.
McCarthy gets credit for crafting a decent backup system QB in Flynn who got three straight rapid bum's rushes out of three other organizations. Works for the Packers in a pinch, so thanks for that.
I believe that about covers it over a 20 year career as a QB coach, OC and head coach.
Oh wait, Elvis Grbac had one very good year...two years after McCarthy left KC.
Holmgren had to keep Brett Favre from flying off into space. That may be the greatest accomplishment of all.
When I think of McCarthy's virtues the words that come to mind are "consistency", "continuity", "process", "program"...foundational things. That's big.